In mobile communication systems represented by a cellular communication system or radio LAN (Local Area Network) system, random access areas are provided in the transmission domain. When a terminal station (hereinafter “UE”) implements an association request to a base station (hereinafter “BS”) at first, or when a UE implements a new band assignment request in a centralized control system where, for example, the BS assigns transmission time and transmission frequency band to the UE, random access areas are provided in the uplink. Here, a base station is also referred to as an “access point” or “Node B.”
Further, in systems adopting TDMA (Time Division Multiple Access), which is currently standardized in 3GPP RAN LTE, when the initial association request is implemented (i.e., when the power supply of a UE is activated, and further when handover is performed, when communication is not performed for a predetermined period or when the transmission timing synchronization in the uplink is not established such a case where synchronization is lost due to the channel condition), a random access is utilized in the first process of acquiring uplink transmission timing synchronization, implementing an association request to the BS or implementing a band assignment request (i.e., resource request).
Unlike other channels to be scheduled, reception error and retransmission occur with respect to random access bursts (hereinafter “RA bursts”) transmitted in a random access area (hereinafter “RA slot”) due to signature sequence collision (i.e., transmitting the same signature sequence by a plurality of UEs using the same RA slot) or due to interference between signature sequences. When RA burst collision and reception error occur, the processing delay by acquiring uplink transmission timing synchronization including RA bursts and processing delay for association request processing to BS, increase. Therefore, a reduced collision rate of signature sequences and improved detection performance of signature sequences are required.
As a method of improving detection performance of signature sequences, studies are underway to generate signature sequences from a GCL (Generalized Chirp Like) sequence or Zadoff-Chu sequence of low autocorrelation characteristics and low cross-correlation characteristics between sequences.
In the WCDMA (Wideband-Code Division Multiple Access) system disclosed in Non-Patent Document 1, to prevent collision of preambles and identify transmitted preambles, a reduced collision rate of signatures is realized by providing a plurality (sixteen kinds) of signature sequences that can be transmitted and providing fifteen RA slots that can be selected randomly in twenty milliseconds. Further, in BS, by using code sequences of good autocorrelation characteristics and good cross-correlation characteristics between signature sequences as described above, it is possible to separate and detect individual signature sequences.
Here, a preamble refers to a signal sequence which is known between the transmitting apparatus and the receiving apparatus and which forms the random access channel. Generally, a random access channel is comprised of signal sequences of good autocorrelation characteristics and cross-correlation characteristics. Further, a signature refers to individual components of a preamble pattern, and, here, assume that a signature sequence is equivalent to a preamble pattern.
Further, in the technique disclosed in Non-Patent Document 2, a reduced collision rate of signature sequences and improved detection performance are realized by classifying the initial cell access including RA burst transmission into the processing to start from the network side (i.e., BS side) and the processing to start from the UE side and reporting paging information including system information related to RA burst transmission by RA burst transmission from the network side to the UE.
To be more specific, Non-Patent Document 2 discloses including uplink (“UL”) interference information and dynamic persistent level parameter showing the retransmission time interval or the like, in paging information reported in the downlink, and reporting the paging information to a plurality of UEs one by one or at a time using PCH's (paging channels).
The UE having received the paging information uses the UL interference information to set RA burst transmission power. Further, it is possible to control the error rate of RA burst transmissions and the time intervals of RA burst transmissions using the UL interference information and dynamic persistent level parameter, so that the UE can control the priority of RA burst transmissions and select a more effective signature sequence.    Non-Patent Document 1: 3GPP TS 25.214V6.7.1 (6.Random access procedure), December, 2005 TSG-RAN working Group 2 #49, Seoul, Korea, Nov. 7-11, 2005    Non-Patent Document 2: R2-052769, LG Electronics, “Initial access for LTE” 3GPP TSG RAN WG1/2 Joint Meeting, Athens, Greece, Mar. 27-31, 2006